Light Emitting Diode (LED) is a semiconductor light-emitting device fabricated by employing P-N junction electroluminescence principles. Advantageous in environmental protection, high luminance, low power consumption, long service life, low working voltage and easy integration, the LED is the fourth-generation new light source following incandescent lamp, fluorescent lamp and high intensity discharge lamp (HID) (e.g., HPSL and metal halide lamp).